Generally, dryers are home appliances that are used to automatically dry damp laundry after washing. The dryers are typically categorized into an air exhaustion-type dryer and an air condensation-type dryer based on a drying method. A structure of the air exhaustion-type dryer will be explained as follows.
FIG. 1 illustrates a conventional air exhaustion-type dryer and FIG. 2 illustrates a passage of air flow in the conventional air exhaustion-type dryer shown in FIG. 1.
In reference to FIGS. 1 and 2, the conventional dryer includes a body 1, a drum 3, a driving part and a heater 5. The body 1 has a door 2 formed on a front surface thereof. The drum 3 is rotatable inside the body 1 and a plurality of lifters 4 are projected from an inner circumferential surface of the drum 3. The driving part supplies a rotational force to the drum 3. The heater 5 heats sucked external air to produce hot air.
In addition, the conventional dryer includes an air suction duct 7, a lint duct 8 and a ventilation fan 13. The air suction duct 7 is connected to a rear opening of the drum 3 to guide hot air from the heater 5 into the drum 3. The lint duct 8 is connected to a front opening of the drum 3 to guide damp air exhausted after drying into an air exhaustion duct 15. The ventilation fan 13 is provided in rear of the lint duct 8 to produce a ventilation force. Also, a lint filter 14 is provided at an end of the lint duct 8 to filter foreign substances such as dust, lint and variations of them from the air exhausted from the drum 3.
The driving part for rotating the drum 3 includes a motor 10, a driving belt 23 that winds around an outer circumferential surface of the drum 3, being connected with a driving pulley 11 fastened to the motor 10. When the driving pulley 11 is rotated by the rotation of the motor 10, the driving belt 12 wound around the driving pulley 11 is rotated to rotate the drum 3.
On the other hand, an electrode sensor 30 is provided in a front portion of the drum 3 to detect a drying rate of the laundry. The electrode sensor 30 is formed of two metal plate that are parallel to sense a drying rate of fabric by using impedence, such that the detected drying rate is outputted as a voltage signal. The impedence is produced at both opposite ends of an electrode based on moisture content when the laundry contacts with both metal plates.
More specifically, a microprocessor (hereinafter, a micom) for controlling an overall system of the dryer receives the voltage signal from the electrode sensor 30 and it determines a drying rate of the laundry based on a level of the voltage to control the operation of the dryer.